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| -rw-r--r-- | Mach/mach/ports.mdwn | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/Mach/mach/ports.mdwn b/Mach/mach/ports.mdwn new file mode 100644 index 00000000..54cc12ac --- /dev/null +++ b/Mach/mach/ports.mdwn @@ -0,0 +1,31 @@ +Mach ports are [[capabilities]]. + +A Mach port is a kernel queue. Each port has associated with +it a receive right and one or more send and send-once rights. +A queue can hold a number of messages. Once the queue is full, +the send blocks until their is space to enqueue the message +(this is interruptible via a timeout mechanism). + +A receive right designates a queue and authorizes the holder to +dequeue messages from the queue, and to create send and send-once +rights. + +Send and send-once rights designate a queue and authorize the +hold to enqueue messages (in the case of a send-once right, +a single message). Enqueuing a message is equivalent to +[[invoke|invoking]] a capability. + +Send and receive rights are named using local names. Each +task has associated with it a port address space. A ports +are addressed via this table. Each task thus has its own +private [[NamingContext]] for ports. + +Ports can be [[delegate]]d in an IPC message. When the +receiver dequeues the message, the right is made available +to it. + +A thread can only block receiving on a single port. To work +around this, the concept of a port set was introduced. A receive +right can be added to (at most) one port set. When a thread +receives from a port set, it dequeues from any of the ports that +has a message available.
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